The comprehensive atomic level characterization of systems such as heterogeneous catalysts, pharmaceuticals, nanoparticles, functional materials, etc. often presents a considerable challenge due to disorder and/or dilution of the species of interest. Research in our group centers on utilizing solid-state NMR to investigate the structure and composition of systems that are challenging to characterize with conventional techniques. In particular, we will explore the development and application of dynamic nuclear polarization (DNP) enhanced solid-state NMR spectroscopy for the characterization of materials.
In a DNP experiment the high polarization of unpaired electrons is transferred to magnetic nuclei. DNP represents a revolution for NMR spectroscopy since it can enhance the sensitivity of NMR experiments by several orders of magnitude. This enables NMR experiments previously considered impossible or infeasible and allows the application of NMR to previously intractable systems. For example, we have previously employed DNP enhanced solid-state NMR to improve the characterization of surfaces/interfaces of inorganic materials, observe dilute species and active sites, characterize the solid phases (polymorphs) of pharmaceuticals and to enable the fast acquisition of NMR spectra of unreceptive and challenging isotopes (e.g., 2H, 14N, 15N, etc.). However, there is much room for the improvement of DNP by developing improved methods to dope the sample with the radicals, improving radical polarizing agents, developing theoretical models, extending DNP to new classes of materials, etc. In collaboration with the Prof. Marek Pruski’s group we will utilize the state of the art 400 MHz/263 GHz DNP solid-state NMR spectrometer that was recently installed at the Ames Laboratory. In addition to work on DNP enhanced solid-state NMR we are also interested in developing and applying "conventional" high resolution solid-state NMR techniques by using fast MAS and indirect proton detection to obtain improved resolution and sensitivity.
Students and researchers in my group will primarily work on the applications and/or development of NMR techniques. However, they also gain experience in other characterization and modeling techniques such as EPR spectroscopy, quantum chemical calculations, X-ray diffraction, etc. Students also perform basic synthetic and sample preparations.